Using the system Varia Pulse TF3 (Sima Media Olomouc) 78 young people were examined incl. 39 (28 boys, 11 girls) hospitalised at the Paediatric Clinic with the diagnosis of juvenile essential hypertension, and 39 healthy controls. The variability of heart rate (HRV) was evaluated in all subjects in two supine positions (T1, T3) and in active orthostasis (T2). The authors evaluated the heart rate variability by spectral analysis in three frequency areas - VLF (0.01 - 0.05 Hz), determined by the sympathetic nerve and hormonal systems, LF (0.05 - 0.50 Hz) determined by the parasympathetic nerve. LF (0.05 - 0.15 Hz) influenced by baroreceptor activity and HF (0,15 - 0.50 Hz) determined by the parasympathetic activity. The authors found in juvenile hypertonics, as compared with healthy controls, a drop of the total spectral performance and MSSD as well an increase of activity in the VLF area and reduction of the low frequency (LF) and high frequency (HF) area. The HRF differences between the group of hypertonics and healthy controls were found in supine positions as well as in active orthostasis.

        Key words: juvenile essential hypertension, spectral analysis of the heart rate variability (HRV), autonomic nervous system (ANS), sympathetic drive